1. Field of the Invention
The present invention relates to a compaction apparatus utilizing an inertia force of a flywheel, and more particularly to a screw press.
2. Description of the Prior Art
In recent years, during compaction of a refractory brick, high density compression is required. In this connection, the applicant of the present application has proposed a hydraulic compound press with pre-pressing using a hydraulic cylinder. A vacuum type brick compaction apparatus is provided with a soft skirt, as disclosed in Japanese Patent Publication No. 58-44054.
However, such a conventional type of friction press does not have a highly rated performance.
The conventional friction press has a construction as shown in FIG. 5. A screw spindle 31 is supported by a frame 30 through a female screw thereof so as to be moved up and down. The screw spindle 31 is connected to a ram 34 at its lower end portion so the ram moves up and down along guide rails. A punch 32 is mounted on a lower end of the ram 34 to conduct a compaction operation of the refractory brick in cooperation with a die 33 mounted on the frame.
Mounted on an upper end portion of the screw spindle is a flywheel 35 on an outer periphery of which is provided a leather belt 36. A pair of friction plates 39 are mounted on a counter shaft 38 which is driven by a motor 37. The counter shaft 38 is slidably driven by an actuator 40 so that each of the friction plates 39 is alternately brought into contact with the flywheel 35, whereby the flywheel 35 is rotated in either a forward or reverse direction so as to move the screw spindle 38 up or down.
In the conventional friction press described above, rotation of the flywheel, i.e., pressing operation is conducted through the leather belt 36 so that the leather belt 36 must be monitored by an operator whereby the following problems can occur:
(1) The material of the leather belt 36, which is usually cowhide reinforced with nylon, is not stable in quality. For example, in many cases, the hide varies in length according to the weather variations. Also the material changes in quality under the influence of frictional heat in a lengthy operation which causes the hide to break. Thus is is necessary for the operator to continually check the leather belt 36.
When the leather belt 36 is broken during operation, it is necessary to replace the broken belt with a new one immediately in order to avoid a serious accident. Consequently, the leather belt 36 is usually replaced at intervals of 20 to 30 days. However, even when this replacement is conducted, the operator may still be uncertain that the belt won't break. In addition, it is necessary for the operator to climb to the top section of the press every day before operation to check and tighten the leather belt 36, which requires extra time.
(2) Since the counter shaft 38 rotates above the flywheel 35, there is a possibility that the flywheel 35 will collide against the counter shaft 38 when the flywheel 35 is not sufficiently braked.
(3) The forward and reverse rotations of the flywheel 35 depend only on the frictional force acting between the hide and the friction plate 39. Thus, it becomes impossible to eliminate a time lag, whereby an extra stroke is needed which leads to a longer compaction time. Particularly, as is in recent cases, when a method is is employed that requires re-pressing at least 10 times, it is extremely important to reduce the compaction time.
(4) Since the temperature of the hide increases due to friction, it is not possible to conduct a lengthy operation, and it is necessary to provide down-time in order to cool the hide.
Thus, since it is necessary to check the most important operating mechanism manually, the above-mentioned problems constitute obstacles in developing an unmanned compaction system. Further, such an important mechanism if automatically controlled is not reliable. Since the most important compaction mechanism is controlled in an unstable manner, the press is not reliable.